"Mazza called me and said 'I'm in labor,' and I thought it was a practical joke," Lopez -- who was in Las Vegas at the time -- tells Extra. "Then when my mom and sister started blowin' up my phone and tellin' me it's really happening. There was one flight left and we had to rush to get it, and we barely made it!"

"Mazza is a rock star! She was so tough and so strong during the whole thing," Lopez, 36, says. "I peeked over too much and you don't want to do that cause there was a lot going on right there. It was like a CSI episode. So I went back and this beautiful baby girl came out. She's precious."